Guitar Rig phenomenon

Inconsistent voltage coming out of your outlets can be a source, that's why studios and pro players use things like power conditioners for consistent voltage feeds. High-end gear will pick up on and react differently if there's even a few volts of variance in what's coming from the wall. EVH's magic brown sound, for example, came from using a variac (like a sophisticaded rotary wall dimmer knob or slide) to lower the wall voltage that his Marshall was plugged into.

Cloth wiring in a vintage guitar's harness can retain moisture, increase electronic resistence and subsequently shave off high end. I think that's nitpicking - the amp has a treble knob. I'd expect humidity variance may have effects on speaker cones' response. But that's total conjecture on my part. And surely our moods influence our perception of what we sense. We're fickle, sensitive creative artsy people after all haha

I have heard Eric Johnson play live through many amps, everything from a Fender Deluxe Reverb to his full 3 amp stage rig, and he always sounds like Eric Johnson. Likewise no matter what amp setup I have used over the last 45 years I sound pretty much the. I believe that 90% or more of a player's tone is in their fingers, and sometimes we play well, and sometimes we don't.